This is a good time of year to check your high tensile wire tension on your fences. In late fall the air temperatures are normally at about the mid range point. There will be some expansion and contraction going on with your high tensile wire.
I have noticed, over time, that some of the fences I have built in 100 degree heat of summer will become overly tight in the cold of winter. And, vice/versa, some of the fences I have built in the cold of winter will sag during the heat of summer. Sometimes this is visually noticeable and sometimes not.
Regardless, this is a good time of year to check your tension and adjust your wire tensioner’s appropriately. There are some high dollar precision tension meters available but none that I know of that can be cost justified for measuring tension on your farm fence. There is a very simple one that you can build yourself for around $5. Check it out
Also, some of the tension springs have notches in them that will indicate tension of about 100 pounds per notch. These used periodically can help give you a good feel for the tension.
For 12.5 gauge high tensile wire, I have seen recommendations ranging from 150 pounds up to 250 pounds. Personally I like around 200 pounds – this will not be overly tight but with very little sag either. I like for my wire to be springy and bouncy.
There have been some isolated incidents, in which, line posts have actually bent due to too much wire tension. And, although, a tight wire at 350 pounds may look nice, it is not necessary and probably causes more problems than a properly tensioned wire.
Here is a link to another blog article that goes into more detail about tensioning high tensile wire: http://www.pasturepro.com/blog/2010/06/tensioning-high-tensile-wire/